Filtration apparatus



Patented Sept. 14. 1948 UNITED STATES PATENT OFFICE FILTRATION APPARATUS Qharles Leandro I iightfoot, Jr., Summit, N. J. Application November 21, 1947, SerialNo. 787.371-

6 Claims.

This invention relates to a filtration apparatus and more particularly to'an improved filter funnel assembly.

An object of the invention is to provide a filter funnel permitting rapid and quantitive recovery of the precipitate. Another object is to provide an apparatus having easy access to all of its parts, thereby facilitating the cleaning thereof. A further object is to provide simple means whereby superatmospheric pressure can be applied to the mixture being filtered. 7

These and other oblects will become apparent I from the following description and the accompanying drawing in which one embodiment of the invention is illustrated.

In the drawing Fig. 1 shows a central vertical section of a filter assembly embodying one formof my invention;

Fig. {2 is a horizontal section taken along the line 2-2 indicated in Fig.- 1, and illustrates one suitable form of the filter disc used in my invention. the casing snu ly surrounding the disc being omitted from Fig.2 for the sake of simplicity; and

Fig. 3 shows in central vertical section an accessory device. i. e. a loading device referred to in the specification.

As illustrated in the drawing, the novel apparatus includes a precisely constructed casing or funnel member of upright cylindrical or similar shape having longitudinal walls I I and. a horizontal bottom or shoulder member l2. Said shoulder member has a central opening from which descends a-tubular stem or collar l3. The casing is preferably cylindrical as shown, but it may have any other preferably symmetrical cross-section or base, for example in the form of a square or other polygon. The casing may be of any desired size ranging conveniently from a diameter of about inch to 10 inches or even larger. being preferably of a size for which standard filter papers are available. The side walls ll of the-casing are of correspondingly appropriate height. e. g. l to inches.

The second essential element of the funnel assembly is a piston member movable along the line indicated by arrow 21 and consisting of ejector disc l4 which has a small central opening I5 and a discharge tube or tubular. stem .18 depending therefrom as shown and intended to extend into 2 ance as small as practical between the periphery of disc l4 and the inner surface of walls I I.

As shown in Fig- 1 a filter paper of substantially'the same size as the bore of the cylinder is supported on the upper surface of the piston disc l4 while this disc itself is supported by the shoulder I2 of the casing. The contacting sur-" assure a tight seal.

The filter paper 20, resting on top of disc l4 when in operative position, should be at least large enough to cover all of the circular grooves 2| of disc M. However, where analytical recovery of the precipitate is desired. it is preferred to employ a filter paper 20 which has a diameter slightlylarger than the bore of the casing l I. This oversize paper can be simply put in place by placing it on the upper rim of the casing l l and thereafter depressing it into position by an ap ropriate plunger, e. g. by a du licate of the slidable piston member l4. Alternatively, a separate simple loading device may be used as illustrated in Fig. 3. This device may consist of a cylindrical block divided by a deep circular groove 23 into an inner cylindrical portion or anvil 24 and an outer until paper 20 is placed against disc M, the outer edges of the paper being cupped slightly in the process. Thereafter, the loading deviceis withdrawn and the funnel containing a slightly cu ped filter paper is ready to operate.

This use of slightly oversized cupped filter paper has been found to be so unexpectedly effective as to make the apparatus suitable for analytical work involving the quantitative weighing of precipitates. The unexpectedly complete recovery of the precipitates is apparently due to the fact that when such a cupped filter paper is being pushed from the casing it exerts a positive thrust in the direction of the walls, thereby removing any precipitate adhering to the side walls. Ac-

' readily.

curacy of up to 1 mg. has thus been obtained The pistondisc i4 is provided with an intercommunicating' system of concentric circular grooves 2| and of radial grooves 22 converging into the opening I 5 as shown in Fig. 2 so as to permit a substantial portion of the surface of filter paper 20 to be acted upon bythe vacuum applied from the filter flask ii. The width of the grooves should desirably range between 0.01 inch to 0.025 or 0.050 inch, the maximum tolerable width of the grooves be ng determined as the distance which will not allow the spanning portions of the filter paper to be drawn into the grooves by suction to such an extent as to cause rupture of the paper or otherwise adversely affect the filtration. Thus it will be seen that the ultimate width is ported on disc i2 within cylinder walls ii and vacuum is applied to flask ll, thereby forcing the liquid downwardly through filter paper 20, grooves and opening of disc l4 and tube i0 into flask I'I while the solid precipitate is retained on top of filter paper 20. At the end of the filtration,

the vacuum is disconnected and the funnel assembly removed from flask l1. Thereupon. by pressing upwardly against tube [5 disc i4 is slid out of the casing defined by walls ii in the direction of arrow 21. In this manner the tightly fitting piston disc l4 and/or the filter paper 20,

' which may be of slightly larger diameter than dependent on the strength of the filter pa er I which is intended for use in the funnel. The

a depth of the grooves may be 2 to 3 times their Furthermore, especially in intermediate funnel' sizes, e. g. in funnels of about /2 to 4 inch diameter. the circular grooves 2! can be completely omitted leaving a drainage system consisting only of radial grooves 22 and central opening i5. In still smaller sizes, an opening without any groove system has been found satisfactory,

In still anothermodifiication the grooved disc I'd may be replaced by a perforated disc of equal size or, in case it is not desired to use any filter paper, by a disc of sintered metal or glass, or of porous porcelain, in which case the bearing sure face of shoulder I2 is made narrow and the remainder of the inner surface of the shoulder is beveled or otherwise shaped to form a cavity 26 between the disc i4 and the shoulder l2 to allow the filtrate to pass downwardly through the perforations or pores of the disc l4 into the said cavity and thence through a slot or series of slots 28 into the tubular stem i6. Indeed, even where I disc i4 is merely grooved as shown in the draw-- the vacuum. Where. as described above, a perforated or porous piston disc I2 is used the tubular stem l6 may be replaced by a solid stem pass- .in freely through the collar l3 thus leaving a passa e for the liquid between said stem and said collar.

The casing ll, l2 and disc member I' l are conveniently made of metal such as stainless steel, aluminum or Monel, drawn seamless steel tubing being especially suited for the casing since often no additional machining of the wall surfaces is necessary to assure the required smooth inner surface. However, instead of metal, all-or part of the apparatus may be made from porcelain, glass or suitable plastics. or any desired combination of any of the aforementioned and similar materials.

In the operation of my novel apparatus, a dispers on containing a solid phase dispersed in a liquid phase is poured onto filter paper supdisc M as described, exert a sweeping action along the entire inner surface of walls I i. thereby picking up any precipitate deposited on said walls and thereby bringing about an extremely quantitative recovery of precipitate in a rapid and neat fashion and with a minimum'of scraping.

Thus an important advantage is obtained over filtering devices previously known, such asthe standard Buchner funnel, because in the devices of the prior art the entire precipitate had to be scraped from the funnel by means of a spatula, rubber policeman or the like, or the entire funnel had to be inverted and the precipitate loosened by tapping. Any 01' these awkward manipulations brought about more or less severe losses, caused liquor backwash onto the filter and thereby ruled out the use of such filtering devices in the quantitative preparation of expensive chemicals as well as in analytical work. In contrast to known filtering devices, my novel funnel assembly allows the precipitate to be recovered quantitatively by the expedient of pushing disc i4 into a readily accessible position where it is substantially flush with the upper edge of walls ii, avoiding completely any need for recovering precipitate from the vertical walls in separate manipulations such as washing down and scraping. Also my novel funnel greatly facilitates thorough cleaning thereof.

walls II with precision as described hereinbefore,

a second piston can be fitted to the funnel from above so that mechanical or pneumatic pressure can be applied to the top of the filter cake in order to express liquid from solids which tend to retain much of the mother liquid. In fact, a duplicate unit consisting essentially of disc it with attached tube IE (not provided with any perfora tion 28) can be used for this purpose by inserting it into the cylinder walls Ii in an inverted position, the end of tube 4 being connected to a suitable source of high-pressure gas or fluid.

Furthermore, the movable member consisting of disc I 4 with tube i6 especially where said disc is made of 'sintered or porous material, can be used by itself in the manner of the microchemists filter stick, that is, tube l6 can be attached directly by means of flexible tubing to a vacuum bottle or the like and the member immersed in an inverted position in a vessel containing a suspension from which liquid is to be removed.

Still other modifications of and uses for the filtering device described hereinbefore will be apparent to those skilled in the art. Thus it is to be understood that the embodiment of the invention as shown and described, and the modification thereof mentioned in the specification were given only for purposes of illustration, rather than limitation and it will be understood that many other embodiments of the invention may be constructed which come within the scope of the appended claims. 80, for instance. the principles of the new device described herein may be readily applied to coffee-makers ofthe Silex type, permitting the operator to dispose of coffee grounds thoroughly and all at once, without any need for repeated rinsing and separate handling thereof prior to disposal.

What I claim as my invention is:

1. In a filtering device, the improvement comprising in combination an open-top receptacle having an opening in its bottom and a closely fitting permeable piston member slidably mounted therein, said piston member having a stem depending therefrom, which stem passes through said receptacle bottom opening permitting passage of liquid therethrough and having a length at least sufiicient to move the piston member into flush position with the free edge of the receptacle.

2. In a filtering device, the improvement comprising in combination an open-top receptacle having an opening in its bottom and a closely fitting piston member slidably mounted therein, said piston member being adapted to support a filter paper and having a perforation in axial direction, and coaxially with said perforation a tubular stem depending from said piston member, said stem passing through the receptacle bottom opening and having a length at least sumcient to move the piston member into flush position with the free edge of the receptacle.

3. In a filtering device, the improvement com-' prising in combination an open-top receptacle having an opening in its bottom and a closely fitting perforated piston member slidably mounted therein, said piston member being adapted to support filter paper and having a stem depending therefrom, which stem passes through said receptacle bottom opening permitting passage. of liquid therethrough and having alength at least sumcient to move the piston member into fiush position with the tree edge 0! the receptacle.

4. A filtering device according to claim 2 wherein the upper surface oi the filter paper supporting piston member is provided with a system 0! communicating narrow grooves leading to the perforation in said piston member. 1

5. In a filtering device, the improvement -comprising in combination an open-top receptacle having an opening in its bottom and a closely I fitting permeable piston member slidably mounted therein, said piston member having a tubular stem depending therefrom which stem passing tightly through the receptacle bottom opening. between the receptacle bottom and the piston member an intermediate space surrounding the base of said tubular stem and in this tubular stem at least one perforation connecting said,in-.

termediate space with the tubular conduit in said stem which stem has a length at least sufficient to move the piston into flush position with the free edge of the receptacle.

6. In a filtering device, the improvement comprising incombination an open-top receptacle having an opening in its bottom and a closely fitting perforated piston member slidably mounted therein, said piston member having a tubular stem depending therefrom which stem passes tightly through the receptacle bottom opening, between the receptacle bottom and the piston member and intermediate space surrounding the base of said tubular stem and in this tubular stem at least one perforation connecting said intermediate space with the tubular conduit in said stem which stem has a length at least sumcient to move the piston into flush position with the free edge or the receptacle.

CHARLES LEANDRO LIGHTFOOT, Jn.

REFERENCES CITED The following reierences are of record in the,

file of this patent: 

